Digital video systems generally communicate a sequence of digital images from a source, such as a camera, to a destination, such as a display.
Various system failures within the digital video system may cause a sequence of images to stop or to lock-up, resulting in a ‘freeze-frame’ condition. Such failures may comprise camera lock-ups, electronic lock-ups, communication faults, storage failures, repeated frames, skipped frames or partial frames, etc.
In critical applications, it is important for a video system operator or user to know quickly if a video system has failed. This may be the case where a static image on the operator's display may cause the operator to erroneously conclude that the scene at the source is simply not changing, when in fact the video system is not functioning correctly. These critical applications could comprise security monitoring, medical monitoring, military surveillance, navigation, manufacturing system tracking, etc.
Referring to FIG. 1, a known functional block diagram illustrating a freeze-frame detection system 101 is shown, comprising a camera 110, image encoding system 112, image verification system 152, and a video display 100. The camera 110 is capable of capturing and transmitting video data that includes sequential video frames. The image encoding system 112 includes a source processor 120, memory 130.
The source processor 120 executes coded instructions to encode pixels from the camera 110 with frame detection codes. The video frames containing the encoded pixels can be communicated over a communication link 150 to a display processor 160.
The image verification system 152 receives the encoded video from the image encoding system 112 and utilises the embedded codes to verify video image continuity and detect a freeze-frame when it occurs. The image verification system 152 comprises a display processor 160, as well as memory 170 and storage 180.
The display processor 160 executes coded instructions to extract and verify freeze-frame detection codes from the video frames received via the communication link 150. The verification process includes generating a local version of the next expected code and comparing it with the code extracted from the received video frame. When the freeze-frame detection code extracted from a frame matches the expected code, then the video frame is deemed not frozen and the frame is presented on the video display 100. Otherwise, when the codes do not match, a fault indication may be presented to the operator or user using the video display 100, e.g. a lamp, LED, siren, buzzer, or other indicator of system fault.
For automotive applications, a frozen image can be dangerous if a driver relies on a display showing an image, but the display does not show the actual situation outside of the automotive application or vehicle. If the display simply displays a frozen image, a user of the display may not recognise a problem with the displayed image until it is too late, and an accident may result.